Alterations to our protocol for isolation of fully active and highly purified complement components have been incorporated to allow improved resolution and recovery of C3, C4, C5 and C9. A second stage DEAE-Sephacel column is used in which certain components (P, C3bINA, C2, C7, FB, C6 and C8) obtained now as complex pools from the initial column are rechromatographed under more favorable conditions. This step should generate components more amenable to further purification. Cl esterase inhibitor and C9 obtained from our protocol have been further purified. Polyclonal antibodies of high titre monospecific for many components have been produced in goats. We also have clones that produce monoclonal antibodies to complement components C3 and C3 fragments and also C9. The membrane attack complex (C5b-9) has been prepared utilizing a novel four step procedure. Antibody to the complex is being produced in a goat. Reactivity with neo-antigenic determinants on C5b-9 will be determined by Elisa assay. Trypsin digestion of C3 and subsequent sieve chromatography has generated C3a with vasoactive activity when tested in guinea pigs. C5 has been cleaved with Zx. Generation of C5a was evidenced by isolation of a 15,000 dalton bio-active fragment. When injected into normal human skin typical wheal and erythema reaction was seen.